Acetabular cup prostheses are used in correcting numerous types of acetabular defects. Each defect often presents a different problem such as a deficient host bone or a compromised acetabular wall. Specific hip conditions present other particular problems. For instance, in the case of a revision hip replacement, the surgeon is often faced with an isolated superior defect, an isolated posterior defect, or a combined superior-posterior defect. This bone defect occurs during the process of loosening of the previous prosthesis or during the revision operation when bone cement is being removed. In the case of congenital hip dysplasia, the surgeon is faced with an extremely shallow acetabulum but must try to maximize the stability of the prosthesis, i.e., ream the acetabulum without violating the medial acetabular wall. In the case of acetabular fractures, the surgeon is often faced with a socket that has or will heal in a deformed shape. And, in the case of infection, the surgeon sees the result of the infection as bone loss that produces a deformed and/or deficient acetabulum.
In view of the above-described various bone defects, numerous prostheses have been created including devices for filling bony defects. The prosthesis must be stably seated so that it will not shift or loosen. In the case of a conventional cup-shaped prosthesis, the cup must be embedded deeply enough into the bone so that it will be stable. The cup-shaped prosthesis must be selected with a diameter large enough to span the widest part of the defect and also to be stably imbedded; the larger the prosthesis diameter, the greater the amount of reaming that is typically required. Thus significant reaming is often required to embed the prosthesis; unfortunately, reaming often removes viable bone as well as diseased bone.